PLACENTA. 183 



Its nature is similar to that of the pellicles, which soon after their 

 formation cover almost all sorts of fibrinous concretions. It is 

 not a tissue; it is destroyed by placing it in water, and after a few 

 hours dissolves as readily as all the other membraniform concretions. 



475. A coat of deposit, much thicker, more fragile, and not so 

 smooth as the preceding one, surrounds all the vascular trunks; 

 this is what has given occasion to the belief that the vessels of the 

 placenta ramify in the very substance of the caduca; that the chorion 

 is composed of several coats; that the anhistous membrane lends 

 one lamina to the external and another to the internal surface of 

 the placenta, and that the delicate pellicle of the latter is doubled 

 down between all the fibrillae of its lobes and lobules. The lamellae 

 of which it is composed appear to me to be a concreted product 

 of a peculiar exudation from the womb, the chorion, and its to- 

 mentose portion. In this respect there is some analogy between 

 them and the caduca; but they differ from it in this, that they are 

 not to be seen until a long time after the ovum has reached the 

 uterus, while the anhistous sac forms immediately after fecundation; 

 and also in this, that one is very soft and somewhat elastic, while 

 the others are dry, hard, and break almost as easily as glass. 



476. The glandular bodies, to which Blancardi, Malpighi, and 

 Littre attributed important functions in the placenta, are no longer 

 admitted by any body to exist; those anatomists probably allowed 

 themselves to be deceived by the primitive and natural granulations 

 of the chorion. Notwithstanding the assertions of Warthon, Cruik- 

 shank, Mascagni, Wrisberg, Michaelis, and Schroeger, it is now 

 pretty generally agreed to deny the existence of lymphatic vessels 

 in the after-birth. The same is the case as to the nerves which 

 Verheyen, MM. Ribes, Home, and Bauer tell us they have seen. 



477. However, Dr. Lauth has recently published a work tending 

 to prove that a great number of lymphatic filaments of a peculiar 

 kind pass from the placenta to the uterus. It is true that when we 

 carefully separate the ovum from the womb we perceive an infinite 

 number of small whitish threads, extremely easy to break; but it is 

 also certain that similar threads are to be seen when separating the 

 caduca from the surfaces which it lines, the amnios from the chorion, 

 &c., that these are merely gelatinous or mucous tracts, but not 

 vessels, nerves, nor even cellular filaments. 



478. The blood vessels therefore compose the fundamental ele- 

 ment of the placenta; these vessels are but expansions or ramifi- 

 cations of those of the cord, and like those of the navel string 

 are not developed until after the third week, and then by intus- 

 susception and gradually. 



